Refractory brick



A. J. JACKMAN AL Sept. 9, 1930.

REFRACTORY BRIGK Filed !lay 31, 1928 INVENTORS V `P'atented Sept. 9, `1930 UNITEDSTA i emm J. JAcKM mor mmm Ernte ncncncn, m; GHARLES I.. Jones, or *s BURGH, PENNSYLVANIA, ASSIGNORS ro vEsUvI s cwcI'BIEcoMrAn or sw ssi VALE, PENNSYLVANIA; AcORI-ORATION OF PENnsYLVANIA REFRAC'I'OEY BRICK Application filed May 31, 1928. serial n' o. 28 1,636l r 'The present invention` relates to refractory brick-and more especially to refractory brick for u'se in furnace linings. i Refractory brick such as silica brick, fireclay brick, chrome brick, etc., are used extensively for linings of` various furnaces.` It is common knowledge that refractory brick of this kind when subjectedto long eXposure toiheat or to intermittent heating, and cooling break `off and spall at their faces which are eXposed to the heat of the furnace chamber. The brick u su- "such for example, as the change in crystalline structure of` a slica brick from quartz to cristobalite,-wh en `eXposed to high heat for a considerable period of time. The bricks, when built into a furnace lining, such as that of the furnace wall or roof, are laid side by side so that one face of the brick is exposed' to the heat oftheifurnace chamber. Refractory brick of the kind referred to above have relatiyely: poor, 'heat-conducting capacity, so that there is a relatively steep temperature gradient from the face of the brick into its body. Since the brick are built into a Wall or roof, the isothermal planes a brick are substantially paralleltothe eX- posed` face 'of the brick. In -spall-ing, the clevage planes in general tend to" run along the direction of the isothermal planes, permitt-ing the expfosed face to spall or break ofiz'. The changes in crystalline structure in the brick' take place from the face of: the

brick back into the body of the brick. When a` change. ingthe crystalline structure takes place, as for example, the change from quartz to cristobalite in a silica brick, the change begins at the face of the brick and progresses crystalline materials of j'different character tend toform cleavage plane along which the spalling orcracking tends to occun We have ,found that the spalling ofrefrac p tory brick `may be prevented and minimized when thebrick are used for furnace linings,

by forming a composite brick in which a refractory non-metallicelement of `relatively good heat-conducting materialsis combined with the bodycfthe'brick which; is of relatiVely poor heat-conducting material.

` The heat-conducting elements are preferably made inthe form of rods which lie in a direction generally normal to the eXposed surface of` the brick so as to conductthe heat from the eXposed surface into the body of brick and into the walk These heat conducting rods serve to conduct and difiuse the heat i i into the body of the brick and `flatten out` the temperature gradient which would otherwise be steep in'` the material of the brick near `7 its exposedface. They therefore'mnmze i the thermal stress`es. Thecoiductinggrods .also change the shape of the isothermal planes from flat planes lying `parallel to the exposed face of the brick into generjallyconiical surfaces surrounding the rods.; ;Since the cleavage planes due to thermal stresses ;and to changes in crystalline structure lie 'along isothermal planes, these cleavage planes are likewise changed from fiat planesparallel to and near 'the eXposed faces of ?the brick, into planes of a generally conical shape surrounding the rods andextendng well into the body of the brick. Therefore, if cracking should occur alongsuch planes, there :isiless liabilty ofthe falling away of the material, since a piece of material of generally conical shape which extends well into theibody of the brick will resist separation" 'and spalling off much better than'a` plate of such material having a cleavage plane behind it parallel to and near ,theeXpose-d face of the brick. i i

- In the accompanying drawings, we have shownthree illustrative examples of compositerefractory brick embodying cur invention.

In the'drawingsz` Figure l isa perspective View of one form of brick embodying our inVent-ion; I

Figure 2is asection along the line II-II of Figure 1; i r

Figure 3 is a perspective View of a modification; I

F igure 4 is a section along the line IV-IV of Figure 3;

Figure 5 is an end view showing still another modification; and

Figure 6 is a section along the line Vl-VI of Figure 5.

Referring to the embodiment of the invention illustrated in Figure l, reference numeral 1 indicates the body of the brick which may be of fireclay or silica or any other of the usual materials employed for refractory bricks and which are, in general, of relatively poor heat-conducting Capacity. Either of the end faces 2 of the brick are intended to form the exposed face of the brick as it is laid in the furnace lining. A rod 3 of relatively good non-metallic heat-conducting material is embedded in the brick, and as shown in Figure 1, extends from the exposed face of the brick through to the other side of the brick.

The embodiment of the invention illustrated in Figures 3 and 4- is similar to that shown in Figure 1, except that the conducting rod 3 does not extend to the outside of the face of the brick, but terminates at a point within the brick but near the face thereof, so that the face of the brick is formed of the body material of the brick. This is of advantage in some cases where the furnace gases might attack the material of the heat-conducting rod.

In the embodiment of the invention illustrated in Figures 5 and 6, the heat-conducting rod 3 is of a generally conical shape; Th'e face 2 of the brick is the face which is intended to be exposed at the inside of the furnace lining. The conical shaped conducting rod 3' has an advantage in certain instances as it will tend to lock the brick material which surrounds it at the exposed face of the brick and prevent the material from falling into the furnace in case cracking should occur.

lVhile we have shown three illustrative examples in the drawings, it is to be understood that the invention is not limited to the illustrated forms, but may be emboclied in other forms of bricks and other forms of heat-conducting elements. For example, the bricks may be made in various shapes other than the usual rectangular brick shapes, and we intend the term brick to include various shapes. Similarly, the conducting elements or rods may be made of round cross section, rectangular cross section, or irregular cross section, or may be made of various irregular shapes, depending upon the form of the brick. Also, more th an one conducting element may be combined in a single brick, depending upon its size and shape and upon the size of the conducting elements. While in the illustrated examples the conducting elements are shown as rods which are embedded in the body of brick, the conducting elements may be otherwise combined with the bricks, as for example, they may be applied to the faces of the bricks, since their function is to conduct or transfer the heat into the refractory wall, and such function is not dependent upon any particular arrangement of the conductingelements, although the conducting elements Will, in general, extend. back from the exposed face of the brick.

T ie' Volume of the heat-conducting element or elements will, in general, be some- What less than that of the Volume of the body material of the brick,- usually in the neighborhood of from to of the body material of the brick, although this may vary, depending upon different conditions, such as the thermal conductivity of the material of the brick body and the thermal conductivity of the conducting elements. The better the heat conductivity of the conducting elements, the smaller they may -be made. Also, in general, the poorer the heat conductivity of the brick material, the larger the size of the heat-conducting elements.

lt is usually desired that the refractory furnace wall shall not conduct too much heat, and for this reason, it is preferable to have the greater part of the wall nade up of the relatively poor heat-conducting material of the bricks themselves. Also the material of the heat-conducting elements is usually more expensive than that of the brick material, and for motives of econom the size of the conducting elements is mace no larger than necessary in order to prevent or mininize the spalling.

The heat-conducting elements or rods are made of a non-metallic refractory material of better heat conductivity than that of the body of the brick. We have found that a satisfactory material for this purpose is a mixture of silicon carbide and graphite bonded with a clay bond. A mix containing about 15% of fine granular silicon carbide, about of graphite and about of bonding clay makes a satisfactory conducting rod for use in ordinary fireclay bricks.

The composition of the conducting elements or rods may be varied according to the heat conductivity desired. An increase in the amount of silicon carbide and graphite tends to increase the heat conductivity while an increase in the amount of bonding clay tends to decrease it. While We prefer to use a mixture of silicon carbide and graphite, either of them alone may be used with the clay bond or other good non-metallic refractory heatconducting materials may be used in their place.

In making up a composite brick, We have found a satisfactory procedure to be as folloWs:

The bricks are first molded to shape with rod-receiving holcs in them, and are then airdried. y The refractory rods are molded and air-dried and are then inserted in the holes in the brick. Thecomposite brick thus asi sembled is burned or fired in the usual way, which will tend to bond and consolidate the refractory rod with the bonding material of the brick. The composite 'bricks may,-how-' ever, be made otherwise. For example, the rods may be preformed and the brick material molded around them, and the bricks airdried and burned in the usual way. Or the bricks may be molded, air-dried and burned; and` preformed and likewise air-dried and burned 'conducting rods may be inserted and cemented in place with a suitable grout.

- The shrinkage of the material of the conducting rods during the air drying. and firing of the brick may be controlled by the character and amount of the bonding matethe inventon is not so limited, but ma be otherwise embodied within the scope o the material having embedded therein a rodof.`

relatively good heat-conducting non-"metallic refractory material extending in a direction i generally normal to` the face of the brick which is to be exposedto furnace heat.

In testimony whereof we have hereunto set e our hands.

ARTHUR J. JACKMAN. CHAS. L. JONES.

rial employed in such rods, and can beregulated to coincide with the 'shrinkage of the brick material so that there will be little, if any, tendency to cause ruptnre of the 'composite brick by uneven shrinkage of its parts. As is well known to those skilled in the art of making refractories, the shrinkage of variout bonding refractories, such as silica brick, fireclay brick, chrome brick and siliconcarbide-containing materials, may be regulated by the character and amount of the i bonding material used, such as a bonding clay." In making up the refractory rods, material such as a bonding clay will be selected and used in proper amount so as to give to the rods substantially the-same shrinkage as that of the body of the brick. Any of the well known bonding materials other than clay may, of course, be used, such as tarry bonds 'which are burned in the material;

The non-metallic heat-conducting materials, such as silicon carbide and graohite,`

are highly refractory. They will melt as metal will melt, nor have. a tendency to change their character even under intense heat. By shielding the faces of the conducting rods at the exposed faces of the brick the'conducting rods may be shielded from furnac'e atmospheres which would afiect them, and a furnace lining be formed which, so far as the influences in the fur- `nace chamber are concerned, is the same as n and more uniform burning of the composite brick because they facilitate the heat penetration during the burning of the brick.

While we have illustrated and described the preferred embodiment of our invention, 

